1. Field of the Invention
This invention relates generally to an apparatus for recording a color video signal in which signals resulting from timebase-compressing and time division-multiplexing a pair of chrominance component signals are recorded on a track separate from that of a luminance signal at the same time when the luminance signal is recorded. More particularly but not exclusively, this invention relates to an apparatus for recording a color video signal from which a timebase compressor and expander for time division-multiplexing is removed.
2. Description of the Prior Art
For a recording apparatus such as a camera-in-one video tape recorder and other recording and reproducing apparatus (VTR), such a recording and reproducing system is proposed in which a color video signal is divided into a luminance signal and a pair of chrominance component signals and they are recorded on separate tracks (disclosed in published Japanese patent application unexamined NO. 134891/1981). In this previously proposeed recording and reproducing system, a pair of chrominance component signals, for example, a pair of color difference signals R-Y and B-Y are compressed in timebase to one half (1/2), time division-multiplexed with each other as shown in FIG. 2B and then the compressed time division-multiplexed color signal (hereinafter referred to as a compressed color difference signal) is recorded on a track adjacent to the track on which the luminance signal Y is recorded.
FIG. 1 is a schematic block diagram showing a practical example of a prior art recording apparatus 10 which can realize such recording system.
Referring to FIG. 1, in the recording apparatus 10, a luminance signal Y containing a horizontal synchronizing pulse P.sub.H and applied to a terminal 1 is supplied to an adder 2 in which it is added with a first synchronizing signal (pulse)P.sub.Y which is used to match the timings between the channels. The synchronizing pulse P.sub.Y is added to the second half portion of, for example, a horizontal synchronizing pulse P.sub.H to have a polarity opposite to that of the pulse P.sub.H as shown in FIG. 2A.
The reason why the pulse P.sub.Y of positive polarity is inserted is to facilitate the synchronizing separation of this pulse P.sub.Y and to prevent a spurious periodic pattern from being produced in a low band component of the luminance signal Y by the pulse P.sub.Y thus avoiding a moire.
In FIG. 2A, W.sub.H represents the pulse width of the pulse P.sub.H and pulse P.sub.Y and in this example, the pulse width of the synchronizing pulse P.sub.Y is selected to be 1/2W.sub.H.
The luminance signal S.sub.Y added with the synchronizing pulse P.sub.Y is supplied to and frequency-modulated by a frequency modulator 3 and then recorded on a recording medium, for example, a tape 4 by a head Ha.
On the other hand, red and blue color difference signals R-Y and B-Y are supplied to a timebase compressor 40 in which their timebases are respectively compressed to 1/2 and they are time division-multiplexed with each other to thereby form compressed color difference signals (R-Y)' and (B-Y)'. The compressed color difference signals (R-Y)' and (B-Y)' are supplied to and added with a second synchronizing signal (pulse)P.sub.C in an adder 6, thus a compressed color difference signal S.sub.C shown in FIG. 2B being formed.
The second synchronizing pulse P.sub.C is inserted into the same position in time as the position at which the first synchronizing pulse P.sub.Y is inserted in order to match the timings between the channels. In this example, the second synchronizing pulse P.sub.C is inserted into the compressed color difference signals (R-Y)' and (B-Y)' so as to have a negative polarity.
The compressed color difference signal S.sub.C is supplied to and frequency-modulated by a frequency modulator 7 and then recorded on the tape 4 by a head Hb. In this case, the record track in which the compressed color difference signal is recorded is formed so as to become adjacent to the record track in which the luminance signal S.sub.Y is recorded.
In the recording apparatus 10 having a so-called E--E (electronic-editor) function to be able to confirm whether the compressed color difference signal S.sub.C or the like is normally recorded on the tape 4 or not, the compressed color difference signal S.sub.C must be expanded in timebase once so that a timebase expander that is same as the timebase compressor must be prepared.
However, this timebase expander is used only in the E--E mode, this timebase expander becomes wasteful and a peripheral circuit for driving the timebase expander is increased, thus enlarging the circuit scale considerably.
Further, when such E--E function is applied to a recording and reproducing apparatus having a playback function, the reproducing system thereof requires a similar timebase expander and hence similar defects can not be avoided.